MacBook Air black screen and keyboard not working

I'm looking for some help. I used my MacBook Air earlier today no problems, I shut it down as normal but when I turned it back on tonight the screen is black and the keyboard appears to not be working either. I've tried restaring it holding the shift key but all that happens is the shift key light stays on and will not go off. If I turn it on without the shift key then the light will not come on the shift key. I'm so confused??? Any help would be appreciated :-)